In spite of the major advances in mass spectrometry during the past 10 years which have extended this technique to a wide variety of biological compounds with unparalleled sensitivity and specificity, and the fact that the University of Colorado Health Sciences Center (UCHSC) is a major research institution, there are no electrospray ionization (ESI), tandem quadrupole (MS-MS), or high resolution matrix assisted laser desorption instruments on this campus and none available to UCHSC investigators in the Denver area. In order to address this major shortcoming and to support several current NIH-funded projects, a group of six major users are requesting funds to purchase a versatile ESI MS-MS instrument which will fulfill current analytical needs and also serve to enhance the general awareness among UCHSC investigators that mass spectrometry can solve a wide variety of biochemical and biomedical problems. Administrations at UCHSC have provided excellent facilities and strong financial support for this acquisition to assure its efficient and long-term operation. The major use group consists of Drs. John A. Thompson, Paul V. Fennessey, Brad K. Bendiak, Charles S. McHenry, Roy B. Jones, Andrew S. Kraft, and James L. McManaman. Dr. Thompson will utilize the ESI MS-MS to investigate reactive metabolites of cytotoxic phenols, including electrophilic quinone methides which alkylate proteins and DNA, and peroxyquinols which oxidize methionine residues in proteins. Dr. Fennessey will utilize the instrument for ongoing studies on inborn errors in metabolism in pediatric subjects, specifically disorders results in elevated acylcarnitine levels. His group is also involved in protein and peptide analysis and those studies will be greatly facilitated by ESI MS-MS. Dr. Bendiak will be performing structural analyses of oligosaccharides released from human glycoproteins, and oligosaccharides that are sequentially degraded from the reducing end. Dr. McHenry will be examining recombinant subunit proteins of DNA polymerase and establish sites of co-or post-translational modification. He will also identify sites of interaction between subunits through studies with cross-linked peptides. Dr. Jones and Kraft will utilize ESP MS-MS to study the pharmacokinetics and metabolism of complex antineoplastic drugs in physiological fluids. Dr. McManaman will be examining the structures of peptides from aldehyde oxidase and xanthine oxidase to determine sites of post-translational modification and oxidative damage.